1. Field of the Invention
This invention relates to novel organometallic acrylamide compositions that result from the reaction of an azlactone and an organometallic nucleophile. The reaction products of the invention encompass compositions that are especially useful as antifouling and antimicrobial agents.
2. Description of the Related Art
The fouling of surfaces in marine and terrestrial environments has been a long standing problem. Submerged marine substrates in aqueous media such as ship-bottoms, oil platforms, fishing nets, and floodgates have been scarred by microbes including arthropods such as barnacles, coelenterates such as hydras, annelids such as hydroides, diatoms such as fine algae, blue-green algae, green algae, brown algae, and various kinds of bacteria colloquially referred to as slime. These fouling problems, traditionally most acute in the oceans and seas, have extended even into fresh water bodies such as the Great Lakes of North America which have experienced an infestation by mollusks, commonly referred to as zebra mussels (Dreissena polymorpha163 ). These mollusks pose a serious problem to submerged aquatic substrates upon which they attach.
On the other hand, terrestrial substrates, such as statues, stone monuments, signs, building facades, tombstone markers, wood decking and rooftops are also prone to fouling by algae growth in particular. Large expenditures of resources are devoted by private, public and commercial interests in attempts to combat these microbial and fouling problems.
For example, the removal of microbes can be implemented by mechanical cleaning. However, this mode of restoration of surfaces after they have already been attacked by microbes can be costly, and it also can create health and safety hazards to the workers. As can be understood, preventive measures would be more desirable in many cases in combating microbial growth as opposed to taking remedial action. Towards this end, the application of antifoulant paints or coatings as a pretreatment of surfaces susceptible to fouling or microbial growth problems has come into widespread usage as a method to discourage and control microbe infestation. More detailed information concerning antifoulant paints and coatings is described by A. D. Wilson, J. W. Nicholoson, and H. J. Prosser, "Surface Coatings-1", Elsevier Applied Science Publishers LTD : New York, 1987, pp. 17-67; and "Surface Coatings Vol. 2-Paints and Their Applications", Chapman and Hall LTD: New York, 1984, pp. 508-514.
Numerous developments of novel antifouling systems have been proposed. For instance, in U.S. Pat. No. 5,192,451, the use of a water soluble dialkyl diallyl quaternary ammonium polymer (polyquat) is reported to be effective in controlling zebra mussels in ship ballasts. U.S. Pat. No. 5,192,603 teaches an elastomeric undercoat used to reinforce a fouling resistant silicone rubber topcoat. Clare et al. reported investigations on naturally-occurring molecular approaches to providing nontoxic antifoulants in Invertebrate Reproduction and Development, 22:1-3, 67, 1992. Clare et al. discuss the use of certain diterpenes extracted from living organisms as barnacle settlement inhibitors, but, concluded that the potential costs in either isolating in sufficient quantity or synthesizing these compounds was prohibitive to their commercial use as antifoulants.
In general, certain organometallic compounds including copper, zinc, and tin as central atoms have also been incorporated within antifouling systems as biocides. Many of the known organotin biocide compounds are described by A. D. Wilson, J. W. Nicholoson, H. J. Prosser, "SURFACE COATINGS - 1", Chapter 2: "Organotin-Based Antifouling Sysytems," Elsevier Applied Science Publishers LTD: New York, 1987, pp. 17-67; and "Surface Coatings Vol. 2 - Paints and Their Applications", Chapman and Hall LTD: New York, 1984, pp. 508-514. These biotoxins are thought to prevent fouling by interfering with the ability of marine organisms to attach to submerged structures, either by weakening or killing the organism.
Typical antifouling paints contain one or more marine biotoxins which are dispersed in a resin carrier, such as disclosed in U.S. Pat. No. 5,246,913. To achieve a lethal concentration of biotoxin to microbes at the water-substrate interface, such paints rely on diffusion of the biotoxin through the resin to the paint surface. There is a drawback observed, however, in that the rate of diffusion of the biotoxin from the surface into the surrounding water is much faster than the replenishing rate of diffusion of the biotoxin from the bulk resin to the surface. As a consequence of this diffusion rate dynamic, the surface concentration of biotoxin drops below the lethal limit needed to effectively prevent microbial growth thereon before all of the biotoxin in the paint is depleted.
Trisubstituted alkyl and aryl tin compounds are generally more toxic than di- or mono- substituted organotins. Among trisubstituted organotin compounds, propyl, butyl, pentyl, phenyl, and cyclohexyl moieties are generally considered the most toxic to microorganisms. The action of these molecular species as it relates to biocidal activity is described by J. J. Cooney and S. Wuertz in J. Ind. Microbiol., 4, 375, 1989. In particular, nonpolymerized tributyl tin compounds have been used extensively in the last decade as antifouling agents due to their high activity against algae and fungus. Inadvertent run-off and excessive marine applications of tributyl tin compounds are now linked to adverse environmental effects which have not gone unnoticed by regulatory authorities in a number of countries. In fact, in 1988, the United States' Environmental Protection Agency (EPA) classified tributyl tin compounds as restricted-use pesticides, and it presently is illegal to use tributyl tin compounds in antifouling systems such as marine paints.
Recent advances have been made to develop ablative or "self-polishing" paints that typically utilize biocidal polymers based on (meth)acrylic acid which has been esterified with bis(tributyltin) oxide. This method reportedly reduces the toxicity of tributyl compounds by attaching the biocide to a polymeric backbone. In the thus-formed polymers, such as described in U.S. Pat. No. 4,012,392, a slow hydrolysis of the tin ester in water is provided to not only release the biotoxin into the surrounding aqueous environment but which also causes the gradual disintegration and sloughing off of the outer layer of the paint; thereby continuously replenishing the amount of available biotoxin at the water-surface interface. One drawback of these above compounds are that the moieties on the organotin species are not considered maximal for achieving the most efficient antifouling action. Furthermore, (meth)acrylates often polymerize at slow rates and provide polymers with the biocide which possess inadequate thermal and hydrolytic stabilities.
The synthesis of a tributyltin-4-acryloylamino benzoate and the effect of an incorporated 4-amino benzoic acid as a spacer group on fouling has been reported by R. R. Joshi and S. K. Gupta, Polym. Mater. Sci. Eng., 62, 654, (1990). The monomer and homopolymer formed by the methods of Joshi et al. are reported to show maximum toxicity towards Sarcina lutea and Pseudomonas aeruginosa, respectively. The monomer is described by Joshi et al. as prepared by a multi-step scheme involving esterfication of p-aminobenzoic acid with tributyltin oxide in a dry benzene solvent followed by amidation in the presence of acryloyl chloride in a dry benzene solvent. The polymer thereof is described by Joshi et al. as prepared by polymerizing the monomer with 2-2'-azobisisobutyro-nitrile in 1,4 dioxane. However, the multi-step reaction needed by Joshi et al. to form the monomer is burdensome and onerous. The methodology of Joshi et al. is complicated by the necessary removal and precautions which must be taken to handle the hydrogen chloride by-product generated, and by the use of benzene as solvent. Naturally, a facile one-step synthesis scheme to form either the monomer or polymer which avoids troublesome by-products and solvents would be more desirable.
In general, 2-alkenyl azlactones have been reported to react with certain nucleophiles, such as primary amines and alcohols to afford (meth)acrylamide-functional products. A thorough discussion of the ring-opening reactions of azlactones with certain nucleophiles can be found in a review article by J. K. Rasmussen, S. M. Heilmann, and L. R. Krepski, entitled "POLYAZLACTONES", Encycl. Poly. Sci. Eng., 11, 558-571, 1988. However, this report does not indicate that organometallic nucleophiles, such as organotin nucleophiles, are adaptable or suited to the chemistry.
U.S. Pat. No. 4,852,969 to Babirad et al. discloses silanols as reacted with 2-alkenyl azlactones in a nucleophilic addition reaction to yield silyl 2-amidoacetates and silyl 3-propionates. However, these silicon-based nucleophiles are not recognized as biocides and they do not provide antifouling or antimicrobial action. Instead, the reaction products of the above-mentioned Babirad et al. patent were stated to be useful as a means of providing well-adhering claddings to siliceous cores for light transmission in a fiber optics construction. Further, the Babirad et al. disclosure does not suggest the use of nucleophiles other than certain silanols. These silanols are customarily characterized as metalloids, and do not come under the traditional definition of organometallic materials, such as defined by Orchin et al., "THE VOCABULARY OF ORGANIC CHEMISTRY," John Wiley & Sons, New York, 12.100, page 432, 1980.
More recently, U.S. Pat. No. 5,246,913 to Hsu describes a use of non-organometallic-based synergistic antimicrobial and biocidal composition comprising 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one and one or more commercial biocides to purportedly provide a more effective and broader control of microorganisms in various industrial systems.
U.S. Pat. No. 4,820,748 to Nippon Paint Co., Ltd. indicates that germanium esters of methacrylic acid are effective against marine algae.
It is believed that the reaction of an azlactone and a organometallic nucleophile to provide a reaction product, including a product affording antifouling or antimicrobial action, has not been previously reported.